This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Variation in animal behavior is the product of gene by environment interactions. Specifically reproductive behaviors among vertebrates are often regulated by chemical signals (e.g., hormones) which are influenced by environmental cues. In many vertebrate species, variation in reproductive behavior exists as alternative reproductive tactics (e.g., male birds obtaining additional reproductive success through extra-pair mating, whereas other males assume a monogamous relationship). Individuals participating in alternative reproductive tactics likely exhibit physiological differences in hormone secretion and could potentially display unique variation in the genetic code. Indeed, unique genetic variation in hormone signaling pathways may provide valuable information for variation in reproductive physiology and development under certain environmental conditions. Currently, most research investigating alternative reproductive behaviors in animals have focused singly on either proximate mechanisms or ultimate explanations for behaviors. Few studies have combined approaches to address potential gene environment interactions influencing differences in reproductive tactics. Thus, for this research we propose three specific aims to study variation in alternative reproductive behaviors in an avian model system. First, we will measure success for individuals pursuing alternative reproductive tactics using molecular genetic analyses of parentage. Second, we aim to identify proximate mechanisms associated with differences in reproductive behavior via measures of hormones in avian eggs and fecal samples. Third, we will use the information obtained from aims one and two to conduct an informed analysis (e.g., identify specific target tissues based on important hormone pathways identified in specific aim 2) of differences in gene expression. Specifically, we aim to identify the molecular basis of hormone action for observed phenotypic polymorphisms (e.g., reproductive tactics).